The present invention relates to a device suitable for insertion into a mammalian body.
Cannula including catheters, stents, and the like have many medical applications. These devices are usually passed into and through a body orifice, incision, peripheral artery, vein, or urogenital tract of a mammalian body and advanced until they reach a desired organ, structure, or cavity within the body.
These devices are available in many forms and are used for a wide variety of purposes, including diagnostic and therapeutic purposes. Among the uses of these devices are the insertion of dyes and medicines into the body; stents such as for urinary or drainage tubes; endoscopes for viewing what is going on in the body; sampling body fluids; monitoring the electrical properties of body organs such as the heart; passageways for insertion of smaller diameter cannula or catheters; and therapeutic techniques such as angioplasty.
A problem experienced with cannulae is inserting them into the desired location without damaging body tissues or organs. A cannula needs to be sufficiently stiff that it can be guided into place, yet at the same time sufficiently soft so as not to damage or penetrate the body tissue. For example, insertion of a cannula into a coronary artery or the colon requires advancement along a tortuous, bent path with sensitive tissue along the path, and in the case of the vascular path, a path having a large number of branch points.
A variety of techniques have been developed to guide a cannula into a desired location. One such technique utilizes a guide wire comprising an elastic material such as a wire. The guide wire is used to negotiate a bent portion of an organ, such as a blood vessel, in advance of the flexible tube that is to be inserted. This is a time-consuming and tedious process.
Other devices have been developed using shape-memory alloys in a cannula. The shape of the shape-memory alloy and thus the cannula is changed upon heating of the alloy. Such a device is shown in U.S. Pat. No. 4,601,283. Other devices directed to insertion of a cannula into a mammalian body through a tortuous path are described in U.S. Pat. Nos. 3,539,034; 3,868,956; 3,890,977; 4,033,331; 4,427,000; 4,452,236; 4,665,906; 4,742,817; and 4,926,860.
Many of these devices suffer from one or more disadvantages, including excessive stiffness of the cannula, complexity of operation such as a need to heat a shape-memory alloy, and lack of adjustability over a wide range of curvatures while the tube is in a body channel.